The inventors herein have developed an engine control methodology that allows efficient engine operation with some of the cylinders operating with substantially no injected fuel and others combusting, for example, a lean air-fuel mixture. This allows the engine to operate at a higher engine load, thereby extending the lean limit of the combusting cylinders.
However, the inventors have also recognized that such operation is only desired in certain operating modes. In other operating modes, other conditions may be required, such as operating all of the cylinders near stoichiometry, or lean of stoichiometry.